Sugar cane is conventionally harvested by manually first burning the cane to remove the leaves, then hand cutting and piling the cane, and finally mechanical grab loading the piled cane into a transport vehicle. When a cane field that has not been burned (green cane) is cut by hand, the output of cut and piled cane is only approximately one-third of that which is achievable by hand cutting burned cane. Therefore, the cost of hand cutting green cane is uneconomical for most applications. As the economies of sugar cane producing areas improves, hand labor for cutting cane becomes difficult to justify. Accordingly, mechanical cane harvesters are being increasingly used to supplement and replace the vanishing hand cutters.
Their are two basic types of machines for mechanically harvesting cane: (1) a soldier-type harvester, and (2) a chopper harvester. A soldier harvester is used for harvesting erect cane, and takes the erect cane into a center carrier where the cane is conveyed through the body of the harvester while remaining vertical. While the cane is erect in the field, the tops of the cane are removed and the cane is base cut at ground level. If the cane is not standing erect, the soldier-type harvester is designed so that its front end lifts the cane to an erect position prior to the cane entering the center carrier for progressing through the harvester in the erect position. The cane is thus lifted into the center carrier and, while held by the center carrier, is topped, base cut, and passed through the carrier in the body of the harvester. After being carried in its vertical position through at least a portion of the body of the harvester, the cane is piled in one or multiple row heaps, where the cane is later conventionally burned to remove the dead leaves on the millable cane stalks. The cut cane is loaded whole stalk into transports by grab loaders. Solider-type cane harvesters are disclosed in U.S. Pat. Nos. 5,379,577, 5,303,533, 4,483,130, 4,380,281, 4,232,775, 4,165,596 and 3,090,183.
While the soldier harvester works quite efficiently in conditions where cane varieties allow the cane to be easily moved to an erect position without burning, the soldier harvester does not work as well in cane fields where the row spacing is less than 5 ft. 6 inches wide, or where burning of the cane on the ground is not allowed. Since the cane is transversely piled whole stalk, a large row spacing is desired to stack the relatively long whole cane stalks. As a practical matter, Louisiana has the only significant location which has the type of cane varieties and field conditions which allow for the effective use of a soldier-type harvester.
Conventional tropical cane harvesters or chopper harvesters are characterized by their bottom first feeding of the cane stalks into the mouth of the harvester. This is followed by a chopper cleaning mechanism which cuts the passing cane and leaves into short pieces. A forced air current is used to remove the free leaves. The chopped cane is conventionally passed through a side loading conveyor and loaded directly into the transport. While a conventional bottom first chopper harvester works reasonably well in a burned cane field where most of the cane is erect, it has more difficulty working in a green, unburned cane field, and also has difficulty working a field with much of the cane in a semi-erect or lodged condition.
Those familiar with cane harvesting operations recognize that as the yield per area of harvested cane increases, more of the cane is fallen and is either semi-erect or lodged, and less of the cane remains erect. While chopper harvesters theoretically are designed to work in green cane fields where cane varieties result in a high yield with more cane stalks being semi-erect or lodged, conventional chopper harvesters are almost never used to harvest green cane, and instead harvest cane predominantly from burned cane fields. Burning standing cane in the field removes most of the leaves, thereby facilitating harvesting of the cane without the harvester becoming plugged with material as it moves through the field. Cane burning is environmentally undesirable, however, since clouds of ash from a burnt field may drift over residential areas, thereby making breathing difficult and creating a significant nuisance by covering patio furniture, automobiles and outdoor plants with a layer of ash.
Those familiar with processing cane have long recognized that burning the cane has a significant and undesirable effect upon the amount and quality of the sugar produced from the cane. From a cane processing standpoint, cane should desirably be brought to the processing plant whole stock and green, with little dirt and cane leaf or top matter. Conventional chopper harvesters which operate in burned cane fields cut the stalks of cane into billets which are typically from eight to ten inches long, thus increasing the likelihood that at least some of the sugar in the cane stalk adjacent the end cuts will become lost or will decompose before processing.
Even then harvesting burned cane, conventional bottom first chopper harvesters have the following problems when the cane is semi-erect or lodged: (1) the inability to remove tops from the cane; (2) the inability to base cut cane efficiently and cleanly; (3) substantial damage to the field and to the planted cane as a result of harvester operations, resulting in future crop yield losses and requiring manual replanting of a higher percentage of total cane area; and (4) substantial harvesting costs due to low production rates and high initial costs of conventional single-row, bottom first copper harvesters.
Due to the above problems, the overall cost of mechanical harvesting burned cane can be higher than a reasonable hand cutting operation. When a chopper harvester attempts to harvest green cane, each of the problems mentioned above for the chopper harvester becomes more pronounced.
A primary problem for bottom first chopper harvesters working in green cane field is the abundance of leaves on the cane. This effects the harvester in two distinct places, namely the front end of the harvester and the body of the harvester. The front end of the harvester must allow the harvester to move through fallen down and windblown green cane in a continuous fashion without choking the cane prior to feeding the cane into the harvester. While conventional bottom first chopper harvesters may move reasonably well through some burned cane fields, bottom first chopper harvesters typically encounter extreme difficulty in green fields because of the abundance of cane leaves at the front end of the harvester. Moreover, once cane is in the body of a harvester, the harvester must clean the cane without choking by first removing the leaves from the cane stalks and then removing the leaves from the body of the harvester.
Conventional chopper harvesters do not have adequate mechanical devices to separate the leaves from the cane stalks while the green cane passes through the harvester. More particularly, conventional chopper harvesters have a topping mechanism that is far out in front of the cane intake into the body of the harvester and is operationally independent of the crop divider scrolls. Conventional crop dividers cannot therefore lift and feed much of the semi-erect or lodged cane into the topping mechanism. If tops are not efficiently removed at the front end before they enter the mouth or intake of a harvester, the body of the harvester must then accommodate this extraneous material, which becomes particularly difficult in wet conditions. Some method of effectively and more efficiently topping green cane is desirable to facilitate removal of more of the cane tops prior to the cane entering the body of the harvester.
The distance separating adjacent rows of cane caused by the crop dividers scrolls on each side of conventional single-row chopper harvesters is typically not sufficient to fully separate the harvested row from the adjacent row. Accordingly, the leaves from an adjacent cane row with lodged cane become intertwined with leaves from the harvested row. Also, conventional dividers scrolls are substantially vertical with respect to the ground when working in the field. Conventional divider scrolls thus do not efficiently lift or transversely separate adjacent rows of cane, thereby impeding free movement of the harvester through a green cane field.
As the front of a conventional bottom first chopper harvester moves through fallen green cane, it pushes the tops of the cane in the same direction that the harvester is travelling. The harvester attempts to separate a leaf from its stalk of cane prior to the cane entering by pulling in an upward direction relative to the stalk, which is a much more difficult leaf removal operation than pulling perpendicular to the stalk or downward relative to the stalk. The action of conventional bottom first chopper harvesters in pulling leaves upward relative to the stalk practically restricts forward movement of the harvester through the cane field by pulling cane roots from the ground. This action also intertwines the leaves of adjacent cane rows by lifting the leaves in a direction toward the top of the cane stalks. It then becomes necessary to cut through an accumulation of intertwined leaves and cane to separate adjacent rows, thereby limiting forward movement of the harvester. Cutting apart adjacent rows of cane is conventionally done with a vertical crop divider knife located near an upper portion of each crop divider scroll. This action of a crop divider knife results in a substantial amount of good millable cane being left in the field.
Conventional bottom first chopper harvesters remove leaves from the cane within the harvester by chopping simultaneously through both the cane and leaves. Conventional chopper harvesters blow away free cut leaves, but cannot blow away that part of the leaf which is still attached to the stalk or is trapped by the passing cane. Therefore, the cleaning efficiency of a conventional chopper harvester becomes a function of how short the cane billets are cut. As cane billets are shortened in length, the cane is cleaner. However, shorter billets result in more juice loss and juice deterioration adjacent the many cut ends. Also, more pieces of good millable cane get sucked out of the harvester with the leaves.
The disadvantages of the prior art are overcome by the present invention. An improved chopper-type harvester is hereafter disclosed suitable for harvesting tropical cane. Most importantly, the harvester of the present invention is able to move efficiently through unburned or green tropical cane fields with semi-erect or lodged cane, and outputs cane which may be more efficiently used by the cane processing facility.